FIGURE 8.

San1 functions preferentially with Ubc1 over WT Cdc34. A, San1 peptide multi-turnover ubiquitylation reactions were carried out in the presence of KR San1 and either WT Ubc1 alone, WT Cdc34 alone, or Ubc1 and WT Cdc34 in combination. Notice that reactions with Ubc1 show intense high molecular weight smears corresponding to long polyubiquitin chains on substrate in comparison with the reaction containing WT Cdc34 alone. B, quantification of the conversion of San1 peptide substrate into products containing one or more ubiquitins. Notice that substrate is converted to product more rapidly in the presence of Ubc1 than with WT Cdc34, and the reaction with both Ubc1 and WT Cdc34 does not further enhance product formation in comparison with Ubc1 alone. Error bars represent the S.E. of measurement derived from duplicate data points.